massage à trois
n.— «Sometimes, though, they let unwitting customers become participants in what one might call a massage a trois: While Mathilde washes one man’s hair, her husband kneels and begins biting her buttocks through her thin cotton frock.» —“To have, to hold and to cut hair Kinky ‘Husband’ needs a good trim” by Bill Morrison News & Observer (Raleigh, N.C.) Oct. 16, 1991. (source: Double-Tongued Dictionary)
Further reading
Susan from Virginia Beach, Virginia, shares the phrase her mother used when the kids refused to eat: It’ll grow hair on your back teeth. This supposed motivator likely blends two older traditions: a German idiom, Haare auf den Zähnen haben...
To describe something tiny or insignificant compared with something vast, you might reach for phrases like a drop in the ocean or a drop in the bucket. In Mandarin, there’s an equally picturesque phrase that translates as nine cows, one hair, 九 牛 一...